1. Field of the Invention
Embodiments of the invention relate generally to the field of optical light guides and, more particularly, to non-imaging, light collecting and emitting apparatus, methods, and applications. Even more particularly, embodiments of the invention relate to a light collection apparatus and light guide for use in a concentrated photovoltaic (CPV) solar energy system, as a light emitting apparatus, and other applications.
2. Related Art
Solar energy is an important part of the renewable energy solution. Concentrated photovoltaics (CPV) have the potential to provide a source of cost effective and clean energy. By concentrating solar energy with optics, less photovoltaic (PV) material is used, reducing cost, since PVs are expensive and energy-intensive to produce compared with optical components.
FIG. 1 illustrates the general construction of a planar light guide system as described in the related art in relation to a standard reference coordinate system. Incident light 1 from a distant, extended source (e.g., solar radiation) propagating generally in the (−)y direction is concentrated (e.g., light 2) by a lens 3 and injected into the light guide 4 via a light injection element 5 on or in the face of the guide. The light thereafter propagates generally in the z-direction towards an exit end (edge) 6 of the light guide. The discrete light injection element 5 is a surface portion of the light guide apparatus that may be made by a partial transverse lateral cut extending from a region of the bottom surface 7 of the light guide. Depending upon the tilt angle of the light injection element, the index of refraction of the light guide, and the index of refraction of the external interface of the injection surface, radiation may be totally internally reflected from the face of the light injection element.
In CPV applications, a general object of the system is to collect as much solar radiation as possible and concentrate that radiation as much as possible for input to a PV cell located at an output edge of the apparatus. The presence of the light injection elements results in a non-ideal light guide since light propagation through the transport structure is hindered by interactions with downstream light injection elements. Light loss can occur by absorption or scattering at a light injection element, out-coupling of light at a light injection element, or étendue dilution from interaction with a light injection element. Further system objectives include maximizing primary concentrator acceptance angle, maximizing injection concentration, maximizing light guide concentration, and minimizing component and system weights and thicknesses.
The inventors have recognized the benefits and advantages of a light collecting apparatus for use in a CPV system that is more efficient, lower in cost, higher performing, and easier to manufacture than previous apparatus, and an apparatus that can collect and emit light for lighting applications.